Warnings that Brexit would reduce British influence in Washington have not come to pass, Lord Mandelson will admit.

Lord Mandelson, once best known as New Labour’s shapeshifting master of the dark arts and a high-profile Remain campaigner, has embarked on another rebranding exercise as the UK ambassador to the US.

Not only did some Brexit warnings fail to materialise, he will say in a speech ahead of Donald Trump’s state visit, leaving the European Union has led to new opportunities for Britain in the US.

“Brexit has freed us to pursue closer US ties,” he will say at a meeting of the Ditchley Foundation on Saturday, according to a draft of the speech shared with the Telegraph.

“Britain has the opportunity to use its regulatory freedom and independence from European law to deepen American investment opportunities.

“This is crucial as, post-Brexit, we need to leverage every advantage we can to spur UK growth and employment.”